There are a number of uses of laminates or foils comprising a water soluble polymer and a water insoluble polymer. One such use is in laundry hampers for hospitals. Such hampers may be made of a relatively strong water soluble polymer. For the laundry hampers the outer layer is relative thick and provides most of the mechanical strength of the hamper. The outer layer is also a water soluble polymer. When the hamper is placed in a washing machine the outer layer dissolves. The inner layer of the hamper is a relatively thin layer of insoluble polymer to protect the water soluble polymer from any dampness in the laundry. The full hamper is placed in a washing machine and the outer layer dissolves. The thin inner layer breaks under the mechanical action in the washing machine. The polymers are then discharged with the water from the washing machine. Of course the hamper technology would have potential use in the disposable diaper industry. This technology might also be applicable in food packaging applications such as for foods which are moistened or cooked in water.
There are a series of patents in the name of Roland K. Belz which disclose similar laminates. In these patents the water soluble layer comprises an acrylate polymer which is soluble only in alkaline or acidic mediums. Representative of such patents are U.S. Pat. No. 4,261,066 issued Apr. 14, 1981; U.S. Pat. No. 4,469,728 issued Sep. 4, 1984; and U.S. Pat. No. 4,671,982 issued Jun. 9, 1987. The Belz patents appear to be mainly concerned with the use of foils in sanitary applications such as covers for toilet seats.
Polyvinyl alcohol is a unique polymer in that it may be used as both a water soluble and water insoluble polymer. The properties of polyvinyl alcohol are discussed at Volume 23, page 849 of the Kirk-Othmer Encyclopedia of Chemistry and Technology. One other advantage that polymers based on polyvinyl alcohol have is that they are biodegradable.
Sulphonated polymers containing aromatic rings have been known for some time. Such polymers have been disclosed in U.S. Pat. No. 3,072,618 patented Jan. 8, 1963 in the name of Albin F. Turbak, assigned to Esso Research and Engineering Company. The patent teaches that such water soluble polymers are useful in a number of applications including thickeners, impregnants, adhesives, soil conditioners and textile-sizes. The patent does not suggest that such polymers could be made into films which would be useful in laminate applications.
More recently sulphonated crosslinked polymers containing aromatic tings have been used as ion exchange resins. However, due to the nature of there use such polymers are insoluble.
The present patent application seeks to provide novel laminates of a water insoluble layer and a water soluble layer.